This apparatus is a dump valve. In a pipeline which flows natural gas, it is not uncommon to accumulate condensate on the inner wall of the pipe. Heavier hydrocarbon molecules and water inevitably become entrained in the pipeline flow. Even through an upstream separator removes most of the condensate, some part of it will flow in the stream as entrained droplets. They can, on change of temperature, condense on the wall of the pipe. If the pipeline passes beneath a body of water, the localized cooling of the body of water forms condensate in the pipeline. The condensate collects in low spots in the pipeline and tends to plug the pipeline. If the liquid volume is sufficient, a severe plugging effect can be achieved, and pipeline efficiency is reduced.
The present apparatus is a dump valve adapted to be installed at a selected location in a pipeline incorporating an operator which is connected to the pipeline. More importantly, the dump valve includes two kinds of valve elements arranged on a common stem. The stem or push rod driven by the valve operator is centered in an axial passage through the valve body, and this enables the dump valve to close, perfecting a hard trimmed seal first and a secondary, soft trimmed seal. This closes the valve to continued flow. The apparatus is arranged so that line pressure across the valve seat assists in closure rather than opposing closure. The soft trim valve element comprises an expandable rubber plug which is supported and positioned so that expansion of the plug occurs in a supported fashion.